Patrilineality

Patrilineality, also known as the male line, the spear side,[1] or agnatic kinship, is a common kinship system in which an individual's family membership derives from and is traced through his or her father's lineage. It generally involves the inheritance of property, rights, names, or titles by persons related through male kin.

A patriline ("father line") is a person's father, and additional ancestors, as traced only through males.

By the 21st century most European monarchies replaced their traditional agnatic succession with absolute primogeniture, meaning that the first child born to a monarch inherits the throne, regardless of the child's sex.

Variations of the Salic Law, generally understood in modern times to mean exclusion of women as hereditary monarchs, restricted succession to thrones and inheritance of fiefs or land to men in parts of medieval and later Europe. Once common, strict Salic inheritance has been officially revoked in all extant European monarchies except the Principality of Liechtenstein. However it still prevails in the transmission of most European titles of nobility, notably excepting Spain.

The fact that human Y-chromosome DNA (Y-DNA) is paternally inherited enables patrilines, and agnatic kinships, of men to be traced through genetic analysis.

Y-chromosomal Adam (Y-MRCA) is the patrilineal most recent common ancestor from whom all Y-DNA in living men is descended. An identification of a very rare and previously unknown Y-chromosome variant in 2012 led researchers to estimate that Y-chromosomal Adam lived 338,000 years ago (237,000 to 581,000 years ago with 95% confidence), judging from molecular clock and genetic marker studies.[2] Before this discovery, estimates of the date when Y-chromosomal Adam lived were much more recent, estimated to be tens of thousands of years.